Process of hardening the cutting portions of cutting-tools



J. WHITAKER.

- PROCESS OF HARDENING THE CUTTING PORTIONS OP CUTTING TOOLS.

APPLICATION FILED AUG. 23, 1910. RENEWED MAY 15, 1914.

Patented M21112, 1915.

A-WTED STA onnron.

, JOHN wmmxfin, or nears: warns, PENNSYLVANIA.

'. rnocnss or nannnmn'e cirr'rme roarrons or currrnaroons.

fipeeification of Letters Patent.

7 Application filed August 23, 191.0, Serial No. 578,564. Renewed May 15, 1914. Serial No. 838,896.

North 'Wales, Montgomery count "Pennsylvania, haye invented certain provements in the Process of Hardening the Cutting Portions of Cutting-Tools, of which the following is a specification.

My invention relates .to the manufacture of hack saw blades, and the object of my invention is to produce a hack saw blade having a maximum de ree of flexibility coupled Withfe rtren ely ard teeth i0rming a t in ed e- A, farther part of my invention the method or process of hardening the teeth ,of thesaw. "V

y ention. s m r 1 es ia e m cally' set I orth in the accompany ngdraws in Wh h re is a s e era iae 9 a s ad 13 .2, i a cra s etieee iew of t s e; g is a w Hus a mg es epinthe pr re ati n of he bla s; Fig. 4, is aside elevation of means employed for the purpose of hardening the h, and i 5 5 2 P an View o he s mesubject to v ery rough usage and As is well known, hack saw blades are 4 breakage of the same yery frequent. Attempts have been made to overcome the many ob ections possessed by them, but without v'a l able result. The use of a soft back'yv t aha d edge has not been successtul nor has e use of a softer bla e portlon between the cutting edge and t e back edge, which are-oi a hard temper, proven satisfactory. The saw of myunvent on, on the contrary, possesses flfixlbll lty w th extremely herd te and y p g 9. bend w hout br a n e ni 1. no ma Plane when the forces tending to bend it are rei i" 1 12 fth & 1

n igs. an o ,e. raw1ngs, re resents the blade of a hack saw and 2 tlie teeth of the same. In treating the saw, only the P n of t e h indi at a 3, a e given the final I rdness des rable for proper cutting purposes; the rest of saw blade to the back of the same being spring tempered so as to be flexible. In such ,condib de I m ytake any o in m i iel blade on the market, preierahly one,

ever, having1 a large degree of hardness, made of big carbon steel, for instance, but relat vely brittle, possessing. but little flexis bll ty and tempered with a view to securing a hard cutting teeth as possible, without referenceto the question of flexibility, or I may prepare a blade in any usual or well known manner and harden and temper it by any suitable and eificient process or method. In either instance I draw the temper [of such blade to an extent suflicient to render it spring-like, by any suitable heating means,'and for this purpose I may connect the terminals of a suitable source of electricity with the ends of the saw and Patented Mar. 2, 1915.

pass current through the blade for a length of tim uflicient'for the desired purpose; Fig. 3, llustrating) diagrammatically this 0 erat ion'. 'It will e understood, of course, t any well-known means of drawing the temper may be employed in lieu of the electrical means noted above. The saw is then ready to receive the treatment necessary to haljden the teeth of the same. For this purpose I may mount the saw in a suitable pos tion, preferably with the teeth uppermost and the blade vertically Lfiisposed, in the manner, forinstance, asst w n in Fig. 4, and connect such blade with one terminal of a source of electricity, and such connections may be in the form of wipe contacts 5 lying in position 'f or engagement with the blade as the latter, is moved; Attached to the lated'and the vperiod of contact so proportion'ed that each tooth will be heated to a certain degree, afi'ecting in greater or lessdegree, as may be desired, only that portion of such tooth aboire the root of the same. The heating is momentary; the blade providin' means for quickly dissipating the heat 1;; addition to the air surrounding the toqth, which is of a relatively small cross section. The result is the hardening of the teeth instead of softening as might otheris b if the heating were carr ed'toa greater extent .or' if the mass of metal heatsl as safiie e lr a Prev t a being dissipated quickly enough to harden the steel.

The electrode designed to contact with these teeth is so connected with a source of electricity that a current ismade and broken between its engagement with the successive teeth, in order to avoid danger of arcing, which would destroy the points of tact with the surface of the blade, in order" that as the circuit is made with the blade the current may be dissipated readily as well as the heat generated.

While I have described the use of electriclitiy as the means of heating each tooth to e ect the hardening of the same, it will be understood that such result may be produced with some local treating or heat pro:

ducing agency, other than electricity. The important points of the process are, the hardening of the blade throughout-then drawing to the desired spring temperthen rehardening the point of the teeth, or as much of the tooth as may be desired. The result attained by my process is a saw having a spring tempered blade, teeth with extremely hard cutting points with a body of tough material between such points and the blade; such body preventing the teeth breaking away the spring tempered blade. By preference, the hardening of the teeth is at the points of the same as indicated by the shading in the drawings, but it will be understood that the extent or limits of this hardening may vary within the scope of my invention. For instance, it may be desirable for some purposes to harden only the extreme points of the teeth, while in other instances it may be desirable to harden the teeth almost to the roots of the same. In all instances, however, the hardening of. the teeth will not affect the tempeizan'd flexibility of the rest ofthe blade which will possess the desired spring temper and necessary hardness compatible therewith, nor the tough portion of the saw connecting the teeth and blade.

After the teeth are rehardened, the temper may be drawn in them to whatever. degree of hardness is best suited for the purpose to which they are to be put. This may be done by any of the usual methods such as immersing in sand or oil or other substance heated to the proper temperature.

While I have described my invention with reference to hack saw blades it will be understood that itis not limited thereto and that the same method of treatment to produce the desired result may be applied to band saws, band knives, and to other forms 1. The process of treating cutting tools which consists in tempering the body or blade of the same to the point of spring flexibility, and then hardening the edge of .such spring tempered body by separate momentary applications to isolated portions thereof of a .high degree of heat.

2. The process of treating cutting tools which consists in tempering the body or blade of the same to the point of spring flexibility and then hardening the edge of such spring tempered body by separate momentary applications to isolated portions thereof ofa current of electricity to heat the same to a high degree.

3. The process of preparing hack saw blades which consists in tempering the blade to the degree of spring'flexibility, and then hardening the toothed portion of such blade by separate and momentary applications of a high degree of heat to the pointsof said teeth.

4. The process of preparing hack saw blades which consists in tempering the blade to the degree of spring flexibility, and then hardening the teeth by momentary applications of a high degree of heat to each of said teeth separately and independently.

5. The process oftreating hack saw blades which consists in tempering the body of the blade to the flexibility of spring metal and 1 then subjecting the points of the'teeth to a high degree of heat, such heating being momentary and applied separately to each point, and the engagement of the teeth by the heating agent being alternated by movements of the heating agent or saw with respect to the other.

6. The process of treating hack saw blades which consists in first tempering the body of the blade to the flexibility of spring metal and then subjecting the points of the teeth to the application of a current of electricity, such heating being momentary and of great intensity, and applied separately to each point, and the engagement of the tooth by the current carrying agent being alternated by the breaking of said current.

7. The process of treating cutting tools which consists in tempering the body or blade of the sameto the point of spring flexibility, and then hardenin'g'the-edge of such body or blade by inomentary applicarent of electricity to heat the same to a high 10 I tions to isolated portions thereof of a high degree. degree of heat. In testimony whereof, I have signed my 8. The process of treating cutting tools name to this specification, in the presence 5 which consists in tempering'the body or of two subscribing witnesses. 7

blade of the same to the point of spring JOHN WHITAKER. flexibility, and then hardening the edge of Witnesses:

such body or blade by momentary applica-' MURRAY C. Bonn, tions to isolated portions thereof of a cur- WM. BROWN, Jr. 

